464 LETTERS TO DARWIN, 1843-1859 
tion of European forms in Australia and New Zealand with 
the absence of the converse in England ; our spring frosts 
account for the difference. In South Europe I beheve 
various Austrahan forms are rapidly becoming naturahsed. 
Consider too the current of export of European agricultural 
notions and plants to Austraha and consequent alteration 
of conditions and that nothing of that kind comes back to 
Europe. 
Your letter has interested me more than any you ever 
wrote me (because we are both riipening I Iwpe), but it staggers 
me too. It opens a much wider question upon wliich I have 
often pondered in vain and have hoped latterly to have 
made more of : it is this — are we right in assuming that 
the development of plants has been parallel to that of 
animals ? I sent out a feeler in the concluding notices of 
my review of A. De Candolle where I indicate my view 
that Geology gives no evidence of a progression in plants. 
I do not say that this is proof of there 7iever having been 
progression — that is quite a different matter — but the 
fact that there is less structural difference between the 
recognisable representatives of Coniferae, Cycadeae, Lycopo- 
diaceae, &c. and Dicots of chalk and those of present day, 
than between the animals of those periods and their living 
representatives, appears to me a very remarkable fact. . . . 
